"Fake news" isn't a new phenomenon, it was used even by Hitler to blame the press for their unfavorable view on him. It's the first line of attack used by current and aspiring autocrats.
But in reality, each country has a slightly different problem with "fake" news. The worst of them can only be solved with active counter-intelligence efforts, like in the case of the shadow companies who used highly advanced data analysis methods to find and target vulnerable members of society and change their minds to vote for Brexit, or like in the case of Trump and the Russians who hacked the DNC and the RNC and used the drip-drip method to tire out the voters from Clinton.
There are also cases where the press is very biased. In that case, you won't convince anyone by showing them the actual facts because that makes them stick to their beliefs even more. The best way is less bias and less hysteria. I still remember the Al Gore voters who were sobbing when he lost to Bush, or the republicans who were in tears when McCain lost to Obama. No one cries because their favorite politician lost the race, the American voters have been trained to expect the end of the world every time the other side wins. And that has turned the entire political climate so toxic to the point where it's become impossible for the parties to agree on even the most simple problems.
Therefore, I don't think that crowdsourcing will solve anything. The problem is that people have stopped talking to each other; it's like the Texans who get blamed for being total climate denialists, even though the largest US windmill plant is in Texas. So maybe today is the time for some handholding and listening to the other side instead of trying to create some fancy mathematical methods that promise to uncover the truth one hundred percent of the time.
P.S. Sorry for the ramblings.